The invention relates to a chainwheel of a control mechanism of an internal combustion engine, said chainwheel having an axis of rotation and being formed in one part or a plurality of parts from at least one toothed rim and a wall extending from the toothed rim in the direction of the axis of rotation, and the chainwheel being provided with at least one means for the damping of vibrations and noises, the chainwheel being formed from at least one metallic material and the means for the damping of vibrations and noises being formed at least from a damping material.
There are many different versions of chainwheels of this type. They are designed, for example, in one part, and disk-shaped, from the toothed rim to the shaft seat or are composed in a plurality of parts, for example, from a toothed rim and a wall connecting a hub to the toothed rim. These chainwheels are usually formed from a composite structure of metal and rubber parts. Thus, for example, DE-39 42 761 C2 describes a chainwheel which is divided into an outer toothed rim and a hub. The hub and the outer toothed rim are separated by a free space which is filled with a noise-damping material. The effect of such a design of a chainwheel is that the toothed rim is separated acoustically from the hub and therefore from the engine.
Damping means of this kind are intended for the damping or uncoupling of vibrations and noises which occur due to the contact of the chain of the control mechanism of an internal combustion engine with the chainwheel. Noises and vibrations of this kind can often be reduced only by extremely soft damping means. This leads, in many cases, to undesirable increases in the degrees of freedom of vibration in the control mechanism.
Since such means for the damping of vibrations and noises are arranged mostly between elements subjected to mechanical load, these means, too, are exposed to mechanical loads. Thus, for example, a torsional moment transmitted by the initially described example of a chainwheel from the hub to the toothed rim also has to be transmitted by the noise-damping material. In particular, in the case of damping means of this kind, run-in jolts of the chain, temperatures and contacts with engine oil lead to premature fatigue and deformation and therefore also to the loss of the damping effect.
A component formed by means of a composite structure consisting of one or more metal parts and damping materials is costly to produce. The metal parts have to be manufactured very accurately and, after being manufactured, must be subjected to careful and costly pretreatment. The subsequent method for bonding the metal parts to the damping means, for example vulcanization or injection molding, is complicated.
The object of the invention, is therefore, to provide a chainwheel provided with damping means
which are simple to manufacture,
which act on the chainwheel in a way free of mechanical loads,
which are to the greatest possible extent encapsulated from oil influences, and
which allow the chainwheels to be manufactured cost-effectively.
This object is achieved, according to the invention, in that:
the chainwheel is provided with one or more holes passing axially through the wall,
one or more means for the damping of vibrations and noises are arranged within the diameter of the root circle of the toothed rim and axially on both sides of the wall,
at the same time, the means for the damping of vibrations and noises bear (S) on the wall,
the means for the damping of vibrations and noises engage (S) into the hole or engage through the hole,
a holding element bears in each case, on both sides of the wall, against the means for the damping of vibrations and noises,
the holding elements, between which are arranged the wall and the means for the damping of vibrations and noises, are prestressed relative to one another,
the holding means prestress the means for the damping of vibrations and noises against the wall, without themselves touching the wall or other parts of the chainwheel.
The chainwheel may be formed continuously from a metallic material in one part or a plurality of parts. In this case, the invention is applicable to chainwheels which are both designed to be continuously disk-shaped or composed of a hub, wall and individual toothed rim and are formed in another way. The damping means are arranged outside the effective range of the chain and on both sides of the chainwheel and are thus free of mechanical loads. The damping means are not injection-molded or vulcanized onto the metallic parts. Damping means of this kind may be produced separately for the manufacture of the chainwheel and subsequently be fastened to the chainwheel by simple means. The possibilities for designing such damping means are many and varied. At all events, the damping means engage into a hole or a plurality of axial holes in the wall of the chainwheel or are led through these holes. An arrangement of this type makes it possible, on the one hand, to achieve effective vibration or noise damping and, on the other hand, thereby to premount or orient the damping means during the operation of mounting it on the chainwheel.
Reliable contact with the wall of the chainwheel and therefore a reliable damping effect are achieved in that the damping means are pressed onto the wall by holding elements. The holding elements are formed, for example, by individual disks or by continuous annularly designed disks. The holding elements are braced relative to one another and therefore also relative to the damping means. Reliable contact with the wall of the chainwheel is ensured and the damping properties of an arrangement of this type can be influenced by the amount of the prestress.
The means for the damping of vibrations and noises are simple to manufacture. The possibilities for designing them and the choice of their material are many and various. In preferred embodiments of the means for the damping of vibrations and noises, this means is formed at least from an elastic rubber material or an elastomer. All other elastic materials, such as, for example, some plastic materials, may also be envisaged. In other preferred embodiments of the invention, the means for the damping of vibrations and noises are formed preferably by plugs or disks. The plugs are in each case inserted into a hole in the wall of the chainwheel or are guided there. It is conceivable to assign a disk to a hole on both sides of the wall in each case or to design the damping means in the form of two annular disks.
At the same time, in each case, one of these annular disks is arranged on one side of the wall and engages with a projection or a plurality of axially protruding projections into corresponding holes in the wall.
The holding elements are preferably produced, in the simplest form, from metal sheets or simple injection moldings consisting of a plastic. The metal sheets are to be provided from ferrous materials or other metallic materials. The holding elements are preferably designed in disk form. At the same time, individual disks may be assigned again to each hole, or a holding element is formed by means of an individual annularly designed disk running continuously on the chainwheel.
The means for the damping of vibrations and noises is to the greatest possible extent shielded against the influences of the engine oil if, as one embodiment of the invention provides, the holding elements are designed as encapsulation.
For connecting the holding elements to one another and bracing them relative to one another, there are various clamping elements. In preferred embodiments, there is provision for using screw connections or rivet connections or for welding the holding elements to one another. At all events, the holding elements are pressed under the action of the clamping elements against the elastic material of the damping means, in order to achieve permanent prestress and ensure that these means are held securely. It is advantageous if the clamping elements are guided in the holes or are led through the holes which cooperate with the damping means. The situation is not ruled out, however, where the clamping elements are led through separately introduced holes, for example bores.
Simplified and therefore cost-effective chainwheels are designed, according to the invention, without any encapsulation. There is therefore provision, furthermore, for above-described embodiments of the means for the damping of vibrations and noises to be used without bracing and encapsulation. In embodiments of the invention, the damping means are fastened to the wall of the chainwheel by means of an adhesive bond or the holes initially described are used.